1. Field of the Invention
This invention relates to a flexible container, particularly a flexible container that can withstand high sustained internal pressures and extreme temperature conditions, making it suitable for containing and transporting toxic and other hazardous materials both by ground and by high-altitude aircraft.
2. Description of Related Art
Under new Federal Aviation Administration (FAA), in the United States, testing criteria in the United States, a container must be able to withstand a sustained internal pressure of about 14 psi for at least about 30 minutes in order to be suitable for transporting toxic and other hazardous materials, using air transportation. For example, if an airplane traveling at an elevation of about 42,000 feet is depressurized, the container must withstand a net effect of an internal pressure of about 14 psi in order to remain sealed. Many conventional containers, particularly flexible containers, cannot withstand such high internal pressure. As a result, a conventional flexible container leaks through a closure which sealably closes a container opening, breaks at a weak peripheral seal or deforms or expands at a region and develops an opening, whereby the materials contained within the container leak from the container.
For example, it is very difficult to provide a flexible container that can withstand high internal pressures and maintain a leak-proof closure. To withstand high internal pressures, conventional flexible containers are constructed of relatively thick materials that require a longer sealing dwell time to effect a peripheral seal that allows the internal pressure to approach a limit or maximum strength of the container material. With heavier materials it becomes increasingly difficult to provide a leak-proof container closure.
Thus, leaks develop at a weak portion of the closure or seal joining the materials, particularly when the flexible container is subjected to a high internal pressure. Further, when the thick materials are folded to form a seal about an opening in the container, the walls of the container near the opening do not sufficiently contact each other to form a leak-proof seal. The materials forming the walls of the container have a shape memory or bias force which urges the materials from a sealed position to an initial flat position.
Conventional flexible containers may not be able to withstand extreme temperatures, particularly as they occur at or near endpoints of a range from about −40° F. to about 130° F. , and particularly over a prolonged time period, for example at least about 2 hours.
There is an apparent need for a flexible container which is suitable for shipping or transporting hazardous materials by air.
There is also an apparent need for a flexible container which can withstand a high sustained internal pressure, for example when subjected to decompression pressure effects at high altitudes, and/or where the materials and closure structure can withstand a temperature operating range of about −40° F. to about 130° F. , particularly over a prolonged time period.